The concept of minimally invasive transdermal drug delivery systems has been developed over time to overcome, or at least provide an alternative to, the drawbacks of conventional metal needle drug delivery. These minimally invasive transdermal mucosal drug delivery systems have been designed to allow drugs to pass through the stratum corneum layer of the skin and the epithelial cells of the mucosa thereby enabling drugs to bypass this skin and mucosa barrier and deliver drugs into the microvascularization of the dermis and mucosa or their lower tissues and potentially into systemic circulation.
The present invention relates to such transdermal drug delivery devices. Such devices typically comprise a patch containing a drug to be delivered. The patch typically includes an adhesive layer for adherence to a patient's skin. The drug may be present as a liquid in a reservoir, or in a gel, or may be incorporated into the adhesive layer of the patch. The patch is applied to a person's skin and the drug passes through the skin into the patient's system as well as the dermal, mucosal and transmucosal.
In some drug delivery systems, one removes the stratum corneum layer of the skin in preparation of topical administration of a drug. Removal of the stratum corneum layer is typically done by scrapping the skin with a mechanical device or by repeatedly applying a tape strip to the surface of the skin and then removing the tape to remove the stratum corneum layer of the skin. Both of these methods of removing the stratum corneum layer of the skin are cumbersome and uncontrolled methods utilized in preparation of topical administration of a drug.
Transdermal delivery devices have also been developed which include hollow microneedles which are forced through the stratum corneum. U.S. Pat. No. 6,611,707 B1 to Prausnitz et al. discloses a microneedle drug delivery device having one or more drug reservoirs positioned over a housing which includes an array of hollow microneedles, with a seal located therebetween. An adhesive layer is applied in-between the microneedles at their base, or to an attachment collar or tabs adjacent the microneedles, to facilitate adherence of the device to the skin. The delivery of drug from a reservoir is initiated by removing or breaking the seal and applying a force, such as by pressing the top of the reservoir, to cause the reservoir contents to flow out through the microneedles. The microneedle device includes a feedback means so that the user can (1) determine whether delivery has been initiated, and/or (2) confirm that the reservoir has been emptied. Representative feedback means include a sound, a color change indicator, or a change in the shape of a deformable reservoir. U.S. Pat. No. 6,656,147 to Gertsek is similar to Prausnitz U.S. Pat. No. 6,611,707, but has a housing which forms a collar extending away from the microprotrusion array. A pressure sensitive adhesive is applied to the underside of the collar so that the device is adhered to the skin.
U.S. Pat. No. 6,821,281 to Sherman et al. discloses a transdermal delivery device in which a reservoir is positioned above an array of microprotrusions which are not hollow, but which may include grooves. The microprotrusions are used to scrap skin cells from the skin when the device is moved in at least one direction. Medication forced out of the reservoir and flows down between the array of microprotrusions and into and through the patient's skin.
All of the above microneedle or microprotrusion array devices are relatively bulky and/or rigid devices employing some type of housing for the microneedle or microprotrusion array, and for the ingredient reservoir. The housing is typically made of a plastic material. U.S. Pat. No. 6,656,147 to Gertsek suggests a housing or bladder made of a flexible plastic or rubber like material.
As used herein, “microprotrusion” will be used as a generic term, encompassing microneedles as well as other types of small abrading protrusions. The “micro” portion of this term is usually understood to mean something so small that it can only be seen with a microscope. However, in this art, the micro portion of the term is understood to mean relatively small protrusions which often are typically at least sufficiently large to be seen with the naked eye. As used herein, “transdermal” will be used as a generic term encompassing dermal, mucosa and transmucosal as well.